Fuel cell and method for controlling same

ABSTRACT

The present invention relates to an improved fuel cell and method of controlling same having an anode and a cathode which produces an electrical current having a given voltage and current output and which includes a controller electrically coupled with the fuel cell and which shunts the electrical current between the anode and the cathode of the fuel cell. The invention also discloses a method for controlling the fuel cell having an anode, a cathode and a given voltage and current output and which include determining the voltage and current output of the fuel cell; and shunting the electrical current between the anode and cathode of the fuel cell under first and second operation parameters.

RELATED PATENT DATA

The present application is a reissue of U.S. patent application Ser. No.09/108,667, filed on Jul. 1, 1998, now U.S. Pat. No. 6,096,449, which isa continuation-in-part of U.S. patent application Ser. No. 08/979,853and which was filed on Nov. 20, 1997, and is now U.S. Pat. No.6,030,718.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an improved fuel cell and method forcontrolling same, and more specifically to a fuel cell which includes anelectrical circuit which, on the one hand, prevents damage to theinternal components thereof upon failure of the fuel cell; and whichalso can be utilized to increase the electrical power output of same.

2. Description of the Prior Art

The fuel cell is an electrochemical device which reacts hydrogen, andoxygen, which is usually supplied from the ambient air, to produceelectricity and water. The basic process is highly efficient and fuelcells fueled directly by hydrogen are substantially pollution free.Further, since fuel cells can be assembled into stacks of various sizes,power systems have been developed to produce a wide range of electricalpower output levels and thus can be employed in numerous industrialapplications.

Although the fundamental electrochemical processes involved in all fuelcells are well understood, engineering solutions have proved elusive formaking certain fuel cell types reliable, and for others economical. Inthe case of polymer electrolyte membrane (PEM) fuel cell power systemsreliability has not been the driving concern to date, but rather theinstalled cost per watt of generation capacity has. More recently, andin order to further lower the PEM fuel cell cost per watt, muchattention has been directed to increasing the power output of same.Historically, this has resulted in additional sophisticatedbalance-of-plant systems which are necessary to optimize and maintainhigh PEM fuel cell power output. A consequence of highly complexbalance-of-plant systems is that they do not readily scale down to lowcapacity applications. Consequently, cost, efficiency, reliability andmaintenance expenses are all adversely effected in low generationapplications.

It is well known that single PEM fuel cells produce a useful voltage ofonly about 0.45 to about 0.7 volts D.C. under a load. Practical PEM fuelcell plants have been built from multiple cells stacked together suchthat they are electrically connected in series. It is further well knownthat PEM fuel cells can operate at higher power output levels whensupplemented humidification is made available to the proton exchangemembrane (electrolyte). In this regard, humidification lowers theresistance of proton exchange membranes to proton flow. To achieve thisincreased humidification, supplemental water can be introduced into thehydrogen or oxygen streams by various methods, or more directly to theproton exchange membrane by means of the physical phenomenon known as ofwicking, for example. The focus of investigations, however, in recentyears has been to develop membrane electrode, assemblies (MEA) withincreasingly improved power output when running without supplementalhumidification. Being able to run an MEA when it is self-humidified isadvantageous because it decreases the complexity of the balance-of-plantwith its associated costs. However, self-humidification heretofore hasresulted in fuel cells running at lower current densities and thus, inturn, has resulted in more of these assemblies being required in orderto generate a given amount of power.

While PEM fuel cells of various designs have operated with varyingdegrees of success, they have also had shortcomings which have detractedfrom their usefulness. For example, PEM fuel cell power systemstypically have a number of individual fuel cells which are seriallyelectrically connected (stacked) together so that the power system canhave a increased output voltage. In this arrangement, if one of the fuelcells in the stack fails, it no longer contributes voltage and power.One of the more common failures of such PEM fuel cell power systems iswhere a membrane electrode assembly (MEA) becomes less hydrated thanother MEAs in the same fuel cell stack. This loss of membrane hydrationincreases the electrical resistance of the effected fuel cell, and thusresults in more waste heat being generated. In turn, this additionalheat drys out the membrane electrode assembly. This situation creates anegative hydration spiral. The continual overheating of the fuel cellcan eventually cause the polarity of the effected fuel cell to reversesuch that it now begins to dissipate electrical power from the rest ofthe fuel cells in the stack. If this condition is not rectified,excessive heat generated by the failing fuel cell will cause themembrane electrode assembly to perforate and thereby leak hydrogen. Whenthis perforation occurs the fuel cell stack must be completelydisassembled and repaired. Depending upon the design of fuel cell stackbeing employed, this repair or replacement may be a costly, and timeconsuming endeavor.

Further, designers have long sought after a means by which currentdensities in self-humidified PEM fuel cells can be enhanced whilesimultaneously not increasing the balance-of-plant requirements forthese same devices.

Accordingly, an improved fuel cell is described which addresses theperceived problems associated with the prior art designs and practiceswhile avoiding the shortcomings individually associated therewith.

SUMMARY OF THE INVENTION

A first aspect of the present invention is to provide a fuel cell whichhas a controller electrically coupled with the fuel cell and whichshunts the electrical current between the anode and cathode of the fuelcell during predetermined operational conditions.

Another aspect of the present invention relates to a fuel cell having acontroller which is electrically coupled with the fuel cell and whichshunts the electrical current between the anode and cathode of the fuelcell, and wherein in a first condition, the controller upon sensing agiven voltage and current output terminates the supply of the fuel gasto the defective fuel cell while simultaneously shunting the electricalcurrent between the anode and the cathode of the defective fuel cellthereby effecting an electrical by-pass of same.

Another aspect of the present invention relates to a fuel cell having acontroller which is electrically coupled with the fuel cell, and whichshunts the electrical current between the anode and the cathode of thefuel cell during predetermined operational conditions, and wherein in asecond condition, the fuel cell has a duty and operating cycle, and thecontroller periodically shunts electrical current between the anode andcathode during the duty cycle of the fuel cell thereby causing aresulting increase in the power output of same.

Yet another aspect of the present invention relates to a fuel cellhaving an anode, and a cathode and which produces electrical powerhaving a given voltage and current output and which includes:

-   -   a membrane having opposite sides, and wherein the anode is        mounted on one side of the membrane and the cathode is mounted        on the side of the membrane opposite to the anode;    -   a supply of fuel gas disposed in fluid flowing relation relative        to the anode, and a supply of an oxidant gas disposed in fluid        flowing relation relative to the cathode;    -   voltage and current sensors which are individually electrically        coupled with the anode and cathode;    -   a valve disposed in fluid metering relation relative to the        supply of fuel gas to control the supply of fuel gas to the fuel        cell;    -   an electrical switch electrically coupled with the anode and        cathode and which can be placed into an open and closed        electrical condition; and    -   a controller coupled with the electrical switch, valve and the        voltage and current sensors, the controller upon sensing a given        voltage and current at the voltage and current sensors causing        the valve to be adjusted into a predetermined fluid metering        relationship relative to the supply of fuel gas, and the        electrical switch to assume a predetermined open or closed        electrical condition, and wherein the controller in a first        condition, shunts current between the anode and cathode of the        fuel cell when the electrical switch is in the closed electrical        condition, and simultaneously causes the valve to terminate the        supply of fuel gas to the anode of the fuel cell, and wherein        the electrical switch when placed in the open electrical        condition by the controller causes the valve to be placed in a        condition which allows the substantially continuous supply of        fuel gas to the anode of the fuel cell; and wherein the        controller, in a second condition, shunts current between the        anode and cathode of the fuel cell when the electrical switch is        placed in the closed electrical condition while simultaneously        maintaining the valve in a condition which allows the        substantially continuous delivery of fuel gas to the anode of        the fuel cell during the opening and closing of the electrical        switch.

Yet, still a further aspect of the present invention relates to a fuelcell having a controller which is operable to shunt electrical currentbetween the anode and cathode of the fuel cell during the duty cyclethereof, and wherein in the second operational condition the operatingcycle is about 0.01 seconds to about 4 minutes; and wherein theelectrical power output of the fuel cell increases by at least about 5%,and wherein the duration of the shunting during the duty cycle is lessthan about 20% of the operating cycle.

These and other aspects of the present invention will be discussed infurther detail hereinafter.

DETAILED DESCRIPTION OF THE DRAWINGS

The accompanying drawings serve to explain the principals of the presentinvention.

FIG. 1 is a partial perspective, exploded, side elevation view of a PEMfuel cell module utilized with the present invention and theaccompanying portion of the subrack which mates with same.

FIG. 2 is a partial, exploded, perspective view of a PEM fuel cellmodule which is utilized in connection with the present invention.

FIG. 3 is a greatly simplified schematic representation of theelectrical circuit which is utilized in the present invention.

FIG. 4 is a flow chart of a computer program which coordinates theoperation of the electrical circuit shown in FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

The improved polymer electrolyte membrane (PEM) fuel cell of the presentinvention is best understood by reference to FIG. 2 and is generallydesignated by the numeral 10. The PEM fuel cell, as a general matter,includes a hydrogen distribution frame 11. The hydrogen distributionframe is fabricated from a substrate which has a flexural modulus ofless than about 500,000 lbs per square inch, and a compressive strengthof less than about 20,000 lbs per square inch. As such, any number ofsuitable and equivalent thermoplastic materials can be utilized in thefabrication of same. The hydrogen distribution frame 11 includes a mainbody 12 as seen in FIG. 2. The main body has opposite ends, and a handle13, which allows for the convenient manual manipulation of same. Thehandle is made integral with the main body 12. Still further, elongatedguide members or spines 14 are located on the opposite ends of the mainbody 12. Each spine 14 is operable to be matingly received in, orcooperate with, elongated channels which are formed in the top andbottom portions of a subrack which will be described in further detailhereinafter.

As seen in FIG. 2, the main body 12 defines a plurality of substantiallyopposed cavities which are generally indicated by the numeral 20, butwhich individually are indicated by the numerals 21, 22, 23, and 24,respectively. Still further, a plurality of apertures 25 are formed ingiven locations in the main body 12 and are operable to receivefasteners 26. The main body further defines a pair of passageways 30.The pair of passageways include a first passageway 31 which permits thedelivery of hydrogen gas from a source of same (as seen in FIG. 3) and asecond passageway 32 which facilities the removal of impurities, waterand unreacted hydrogen gas from each of the cavities 21 through 24. Alinking passageway 33 operably couples each of the first and secondcavities 21 and 22 and the third and fourth cavities 23 and 24 in fluidflowing relation one to the other, such that hydrogen gas delivered bymeans of the first passageway 31 may find its way into each of thecavities 21 through 24 respectively. Each of the cavities 21 through 24are substantially identical in their overall dimensions and shape. Stillfurther, each cavity has a recessed area 34 having a given surface area,and depth. Positioned in each of the recessed areas 34 and extendingsubstantially normally outwardly therefrom are a plurality of smallprojections 35. The function of these individual projections will bediscussed in greater detail below. As seen in FIG. 2, the first andsecond passageways 31 and 32 are connected in fluid flowing relationrelative to each of the recessed areas 34. The main body 12 alsoincludes a peripheral edge which is discontinuous. In particular, theperipheral edge defines a number of gaps or openings 36 therethrough.Still further, each passageway 31 and 32 has a terminal end 37 which hasa given outside diametral dimension. The terminal end 37 of eachpassageway 31 and 32 is operable to matingly couple in fluid flowingrelation relative to valves which will be discussed in greater detailhereinafter.

Mounted within each the respective cavities 21 through 24, respectively,is a membrane electrode assembly 50. The membrane electrode assembly(MEA) has a main body 51 formed of a solid electrolyte. This membraneelectrode assembly is described in significant detail in co-pending U.S.application Ser. No. 08/979,853, and which was filed on Nov. 20, 1997,the teachings of which are incorporated by reference herein. The mainbody 51 of the MEA has an anode side 52, and an opposite cathode side53. The anode side 52 is held in spaced relation relative to thehydrogen distribution frame 11 which forms the respective cavities 21through 24 by the plurality of projections 35. This relationship insuresthat the hydrogen delivered to the respective cavities, and morespecifically to the anode side thereof, reaches all parts of the anodeside 52 of the MEA. Electrodes 54, comprising catalytic anode andcathode electrodes are formed on the main body 52. These electrodes arefurther described in the aforementioned U.S. patent application, theteachings of which are also incorporated by reference herein.Additionally, noncatalytic, electrically conductive diffusion layers,not shown, are affixed on the anode and cathode electrodes and have agiven porosity. These noncatalytic electrically conductive diffusionlayers are also described in the aforementioned patent application, butfor purposes of brevity, are not discussed in further detail herein.

As further seen in FIG. 2, the PEM fuel cell 10 of the present inventionfurther includes a pair of current collectors 60 which are received ineach of the respective cavities 21 through 24 respectively. Therespective current collectors are individually disposed in juxtaposedohmic electrical contact with the opposite anode and cathode side 52 and53 of each of the MEAs 50. Each current collector has a main body 61which has a plurality of apertures 62 formed therein. A conductivemember or portion 63 extends outwardly from the main body and isdesigned to extend through one of the gaps or openings 36 which are inthe hydrogen distribution frame 11. This is understood by a study ofFIG. 1. Each conductive member 63 is received between and thereafterelectrically coupled with pairs of conductive contacts which are mountedon the rear wall of a subrack which will be described in greater detail,below. The fabrication of the current collectors is described in detailin the aforementioned U.S. patent application, the teachings of whichare incorporated by reference herein.

As further illustrated in FIG. 2, the PEM fuel cell 10 of the presentinvention further includes individual force application assemblies 70for applying a given force to each of the current collectors 60, and theMEA 50 which is sandwiched therebetween. In this regard, the individualforce application assemblies comprise a cathode cover 71 which partiallyoccludes the respective cavities of the hydrogen distribution frame 11.As seen in FIGS. 1 and 2, the respective cathode covers 71 individuallyreleasably cooperate or otherwise mate with each other, and with thehydrogen distribution frame 11. A biasing assembly 72, which is shownherein as a plurality of metal wave springs, cooperates with the cathodecover and is operable to impart force to an adjacent pressure transferassembly 73. Each of the cathode covers nest or otherwise matinglycouples or engages with one of the respective cavities 21 through 24,respectively, which are defined by the hydrogen distribution frame 11.When appropriately nested, individual apertures 75 which are defined bythe outside surface 74 of the cathode cover, define passageways 76 whichpermits air to circulate to the cathode side of the membrane electrodeassembly 50. The fasteners 26 are received through each of the cathodecovers and through the hydrogen distribution frame that is sandwichedtherebetween in order to exert a predetermined force sufficient tomaintain the respective current collectors 60 in ohmic electricalcontact with the associated MEA 50. The circulation of air through thefuel cell 10 and its functional cooperation with the associated subrackare discussed in significant detail in the aforementioned earlier filedpatent application, the teachings of which are also incorporated byreference herein.

As seen in FIG. 1, and as disclosed in a much more complete fashion inthe earlier filed U.S. patent application which is referenced, above,the PEM fuel cell 10 is operable to be serially electrically coupledwith a plurality of other fuel cells by way of a subrack which isgenerally indicated by the numeral 90. The subrack 90 has a main body 91having top and bottom portions 92 and 93 respectively. The top andbottom portions are joined together by a rear wall 94. Elongatedchannels 95 are individually formed in top and bottom portions and areoperable to slidably receive the individual spines 14 which are formedon the hydrogen distribution frame 11. As best understood in theexploded view of FIG. 1, the subrack 90 is made of a number of mirrorimage portions 96, which when joined together, form the main body 91 ofthe subrack 90. These mirror image portions 96 are fabricated from amoldable dielectric substrate. The functional attributes of the subrack90 are disclosed in significant detail in the earlier filed application,the teachings of which are incorporated by reference herein. As bestseen in FIG. 1, a DC (direct current) bus 100 is affixed on the rearwall 94 of the subrack 90. A repeating pattern of eight pairs ofconductive contacts 101 are attached on the rear wall. Further, firstand second valves 102 and 103 are also attached to the rear wall and areoperable to matingly couple in fluid flowing relation to the hydrogendistribution frame. The respective first and second valves extendthrough the rear wall and connect with suitable conduits (not shown).The first valve 102 is coupled in fluid flowing relation with a sourceof hydrogen 105 (FIG. 3). Further, the second valve 102 exhausts toambient or may be coupled in fluid flowing relation with other systemssuch as a hydrogen recovery and recycling system as disclosed in theearlier filed application. Finally, the fuel cell 10 includes a thirdvalve 104, as shown in FIG. 3, which is disposed in fluid meteringrelation between the supply of hydrogen 105 and the first valve 102. Thesubrack 90 also includes an air distribution system (not shown) andwhich moves ambient air in a predetermined pattern through the fuel cell10. This air distribution system is discussed in significant detail inthe earlier filed application, but for purposes of brevity, is notdiscussed in further detail herein.

Referring now to FIG. 3, a plurality of fuel cells 10 are shown wherethey are serially electrically coupled together to produce electricalcurrent having a given voltage and current output. A shunt controlcircuit 120 is shown. The shunt control circuit 120 includes anelectrical path 121 which electrically couples that anode and cathode 52and 53 of one of the fuel cells together. It should be understood thatthis electrical circuit is present for or otherwise associated with eachof the fuel cells shown in FIG. 3, that is, discrete shunt controlcircuits 120 individually electrically couples the anode and cathode ofeach of the serially coupled fuel cells together. In FIG. 3, however,for simplicity sake, only one of these circuits is shown. Each of theshunt control circuits are electrically coupled to a single shuntcontroller which is generally designated by the numeral 122. As noted,above, the shunt controller is illustrated as being coupled to only oneshunt control circuit. However, the shunt controller would in reality becoupled to numerous shunt control circuits corresponding to each of theserially coupled fuel cells. FIG. 3, as noted above, is greatlysimplified to illustrate the present invention.

The shunt controller 122 comprises a number of individual componentsincluding a pair of voltage sensors 123 which are electrically coupledwith the anode and cathode 52 and 53 to sense the voltage at the anodeand cathode 52 and 53 of each of the respective fuel cell 10. Stillfurther, the shunt controller is electrically coupled to an electricalswitch 124, here shown as being a field effect transistor ofconventional design. A suitable commercially acceptable MOSFET may besecured from Mitsubishi under the trade designated FS100UMJ. The shuntcontroller 122 may be purchased through conventional retail sources. Asuitable controller 122 for this application is the programmablemicrocontroller chip having the trade designation MC68HC705P6A, andwhich may be utilized and programmed to execute the program logic, asshown in FIG. 4, and which will allow the shunt control circuit to reactto the first and second operational conditions of the fuel cell 10, aswill be described in greater detail, below. The shunt controller 122 isfurther electrically coupled in controlling relation relative to thevalves 104 which are disposed in fluid metering relation relative to thesupply of fuel gas 105 (identified as the fuel gas shut-off control).The shunt control circuit 120 has a bypass electrical circuit 126 whichfurther electrically couples the anode and cathode 52 and 53 of each ofthe fuel cells 10 together. The bypass electrical circuit comprises adiode 127. A current sensor 128 is further electrically coupled to thefuel cells 10 to detect the current of same. The current sensor is madeintegral with the shunt controller 122. As noted above, the shuntcontrol circuit 120 is controlled by programmable logic which is setforth more specifically in FIG. 4 and is generally indicated by thenumeral 130. The bypass electrical circuit is operable to shuntelectrical current between the anode and cathode of the fuel cells 10upon failure of the shunt controller 122.

As best understood by a study of FIG. 3, the fuel cell 10 has an anodeand a cathode 52 and 53 which produces electrical power having a givencurrent and voltage output. The controller 122 is electrically coupledwith the fuel cell 10 and is operable to shunt the electrical currentbetween the anode and the cathode of the fuel cell under predeterminedoperational conditions. As earlier discussed, the shunt controller 122includes voltage and current sensors 123 and 128 which are disposed involtage and current sensing relation relative to the voltage and currentoutput of the fuel cell 10 and are further electrically coupled with theanode and cathode 52 and 53 of the fuel cell 10. Still further, theshunt controller 122 further comprises an electrical switch, and whichis shown herein as a field effect transistor 124. The field effecttransistor 124 has open and closed electrical conditions. As will bedescribed in further detail below, the controller 122 upon sensing, byway of the voltage and current sensors 123 and 128, a given voltage andcurrent output of the fuel cell 10, adjusts the valve 104 into apredetermined fluid metering relationship relative to the supply of fuelgas 105. Still further, the controller 122 positions the field effecttransistor in an open or closed electrical condition, based uponpredetermined performance parameters for the respective fuel cells 10.

In this regard, and in a first operational condition where a given fuelcell is performing at or below predetermined performance, parameters orexpectations, as might be the case where the voltage output of the fuelcell is less than about 0.4 volts, the controller 122 is operable tosimultaneously cause the valve 104 to assume a position where itterminates the supply of fuel gas 105 to the fuel cell 10 and places theelectrical switch 124 in a closed electrical condition thereby shuntingcurrent from the anode 52 to the cathode 53 to substantially preventheat related damage from occurring to the fuel cell 10 as might beoccasioned when the negative hydration spiral occurs. This was discussedearlier in the application. Still further, if the electrical switch 124is subsequently placed in the open position, the controller 122 isoperable to cause the valve 104 to be placed in a condition which allowsthe substantially continuous supply of fuel gas to the fuel cell.

In the first and second operational conditions which are describedherein, the predetermined performance parameters of the individual andserially electrically coupled fuel cells 10 comprise selected currentand voltage outputs of the fuel cell 10. These predetermined thresholdperformance parameters may be determined by various means including butnot limited to, experiment; operational history or electrical load, forexample. Additionally, the predetermined performance parameters mightinclude, in the first condition, for example, where the performanceparameters of the fuel cell are just merely or generally declining overa given time interval; are declining or in a range of less than about0.4 volts; or are declining or degrading, generally speaking in relativerelation to the performance parameters of other fuel cells 10 with whichit is serially electrically coupled. This list of possible parameters isnot all inclusive and many other physical and operational parameterscould be monitored, and which would tend to suggest that a selected fuelcell is beginning to fail, and should be disconnected from the stack forrepair or replacement if the shortcoming in performance is severe, or onthe other hand subjected to increased shunting to determine if the fuelcell 10 can be recovered back to the predetermined performanceparameters selected. This is best illustrated by reference to FIG. 4.

In the second operational condition, the shunting circuit 120 isoperable to increase the resulting electrical power output of the fuelcell 20. As discussed above, the fuel cells 10 have predeterminedperformance parameters comprising selected current and voltage outputsof the fuel cell 10. In the second condition, and where the performanceparameters may be merely declining and have not decreased below aminimum threshold, and as was discussed above, the shunting circuit 120is employed in an effort to restore individual and groups of fuel cells10 to the given performance parameters. For example, selective, orgroups of fuel cells 10 may begin to decline in their voltage andcurrent output over time. As this decline is detected by the shuntcontroller 122, the controller 122 is operable, by way of the shuntcontrol circuit 121 to serially, repeatedly shunt the current betweenthe anode and cathode of the degraded performance fuel cells 10 atindividually discrete rates which are effective to restore the fuelcells to the predetermined performance parameters. In another example,where the performance parameters may be merely declining, the controller122 is effective to adjust the duty cycle of individual fuel cells 10 byreference to the declining performance parameters of the fuel cell inrelative comparison to the performance parameters of other fuel cells toimprove the electrical performance of same. As should be understood, theword “duty cycle” as utilized hereinafter means the ratio of the “ontime” interval occupied in operating a device to the total time of oneoperating cycle (the ratio of the pulse duration time to thepulse-repetition time). Another way of defining the term duty cycle isthe ratio of the working time to the total operating time forintermittent operating devices. This duty cycle is expressed as apercentage of the total operating cycle time. In the present invention,therefore, the shunt controller 122 is operable to adjust both theduration of the shunting, as well as the operation cycle time as toselective fuel cells in order to restore or maintain the fuel cellsabove the predetermined performance parameters selected.

As noted above, the inventors have discovered that in the secondoperational condition, enhanced fuel cell performance can be achieved byadjustably, repeatedly and serially shunting current between the anodeand cathode 52, and 53 of the fuel cell 10. In this regard, and in thesecond operational condition, the programmable logic as shown at 130 inFIG. 4 is utilized by the shunt controller 122 to individually,adjustably and periodically open and close each of the electricalswitches 124 that are individually electrically coupled and associatedwith each of the fuel cells 10. These electrical switches 124 may beactivated individually, serially, in given groups, or patterns, or inany fashion to achieve the predetermined voltage and current outputdesired. In this regard, it has been determined that the preferredoperating cycle time is about 0.01 seconds to about four minutes. Whenthis periodic shunting is implemented, it has been discovered that thevoltage output of the fuel cells 10 increases by at least about 5%.Still further, the shunt control circuit 120 is operable to shunt theelectrical current for a duration of less than about 20% of theoperating cycle.

During the second operational condition, the shunt controller 122 causesthe valve 104 to remain in a condition which allows the substantiallycontinuous supply of fuel gas 105 to the fuel cell 10. It is speculatedthat this repeated, and periodic shunting causes each of the fuel cells10 to be “conditioned”, that is, such shunting is believed to cause anincrease in the amount of water that is made available to the MEA 50thereby increasing the MEAs performance. It is also conceivable that theshunting provides a short term increase in heat dissipation that issufficient to evaporate excess water from the diffuser layers which aremounted on the MEA. This evaporation of water thus makes more oxygenfrom the ambient air available to the cathode side of the MEA. Whateverthe cause the shunting appears to increase the proton conductivity ofthe MEA. This increase in proton conductivity results in a momentaryincrease in the power output of the fuel cell which diminishes slowlyover time. The overall increase in the electrical power output of thefuel cell 10, as controlled by the adjustably sequential and periodicshunting of individual, and groups of fuel cells 10, results in theentire serially connected group of fuel cells to increase in its overallpower production. As noted above, the respective shunting controlcircuits 120 are individually operably connected with each of theserially coupled fuel cells 10, and can be rendered operable for singlefuel cells, and groups of fuel cells. Additionally, the duty andoperating cycles of the respective fuel cells may be adjusted in anynumber of different combinations and for individually discretedurations, depending upon the performance of the individual fuel cells,to boost the performance of same; or for purposes of stabilizing thedecreasing performance of a given group of fuel cells or individual fuelcells as the case may be.

OPERATION

The operation of the described embodiment of the present invention isbelieved to be readily apparent and is briefly summarized at this point.

In its broadest sense, the present invention relates to a fuel cell 10having an anode and a cathode 52 and 53 and which produces electricalpower having a given current and voltage output. The fuel cell 10includes a controller 122 which is electrically coupled with the fuelcell 10 and which shunts the electrical current between the anode andcathode of the fuel cell. As noted earlier, the controller 122 comprisesvoltage and current sensors 123 and 128 which are disposed in voltageand current sensing relation relative to the electrical power output ofthe fuel cell 10. The controller 122 further comprises an electricalswitch 124 having open and closed electrical conditions. The controller,in a first operational condition, upon sensing by way of the voltage andcurrent sensors a given electrical power output of the fuel cell 10,places the valve 104 into a predetermined fluid impeding relationshiprelative to the supply of fuel gas 105. In this first condition, theelectrical switch may be positioned in an open or closed electricalcondition, depending upon the predetermined performance parameters ofthe fuel cell 10. As noted above, in the first operational condition,assuming the performance parameters are not met, the controller 122, inresponse, closes the electrical switch. This closed switch shuntscurrent between the anode and the cathode of the fuel cell.Substantially, simultaneously, the controller 122 causes the valve 104to terminate the supply of fuel gas to the fuel cell 10 when thiscondition exists. As noted earlier, when the voltage output of the fuelcell 10 is less than about 0.4 volts, the electrical switch assumes aclosed position thereby shunting voltage between the anode and cathode,while simultaneously causing the valve to terminate the supply of fuelgas 105. As earlier discussed in this application, a negative hydrationspiral can result in excessive heat which causes damage to the MEA 50.In this first operational condition, the shunt control circuit 120 isoperable to shunt the current thereby preventing this damage. Of course,the performance parameters which may trigger the first operationalcondition can include declining performance parameters; or decliningperformance parameters in relative comparison to the performanceparameters being achieved by other fuel cells 10. Still other parametersnot listed herein could also be used.

The shunt control circuit 120, as earlier disclosed, has a passivebypass electrical circuit 126 comprising a diode 127. In the event thatthe shunt control circuit 121 fails in conjunction with a failing fuelcell, the bypass electrical circuit causes the shunt control circuit tobe rendered operational to prevent this aforementioned damage fromoccurring. The diode 127 selected is normally reverse biased when thefuel cell 10 is producing power, and it has no effect on the shuntcontrol circuit 121 under normal operational conditions. As the fuelcell 10 fails, however, and the voltage output nears 0 or becomesnegative, the diode 127 becomes forward biased. The voltage can thentravel through the diode 27 instead of the fuel cell 10. The maximumnegative voltage depends upon the type of diode selected. A Schottkybarrier diode which is commercially available as 85CNQ015, is preferred.These diodes allow high current to flow at approximately 0.3 volts. Thisvoltage limitation limits the maximum positive negative voltage of thefuel cell thereby preventing overheating and subsequent damage.

In the second operational condition, the shunt controller 122, byimplementing the logic shown in FIG. 4 at numeral 130 shunts currentbetween the anode and cathode 52 and 53 of the fuel cell 10 when theelectrical switch 124 is in the closed condition, while simultaneouslymaintaining the valve 104 in a condition which allows the substantiallycontinuous delivery of fuel gas to the fuel cell as the shunt controllerperiodically opens and closes the electrical switch. As noted earlier,the fuel cell 10 has a duty cycle; and an operating cycle of about 0.01seconds to about 4 minutes. The inventors have discovered that theperiodic shunting by opening and closing the electrical switch 124during the duty cycle increases the overall electrical power output ofthe fuel cell 10. This results in the serially coupled fuel cellsincreasing in voltage and current output by at least about 5%. Theduration of the shunting during the duty cycle is less than about 20% ofthe operating cycle.

The present fuel cell 10, and associated circuitry 121, provides aconvenient method for controlling the fuel cell 10 which has an anodeand a cathode 52 and 53 and a given voltage and current output whichincludes,

-   -   providing a supply of a fuel gas 105 in fluid flowing relation        relative to the anode 52 of the fuel cell;    -   providing a valve 104 disposed in adjustable fluid metering        relation relative to the supply of fuel gas 105;    -   providing a controller 122 which is electrically coupled in        current and voltage sensing relation with the anode 52 and the        cathode 53 and which is effective to shunt the electrical        current between the anode and cathode and which further is        coupled in controlling relation relative to the valve 104;    -   determining, by way of the controller 122, whether the voltage        and current output of the fuel cells 10 has a voltage and        current output which is less than a predetermined amount;    -   after the step of determining the voltage and current output,        adjusting the valve 104 by way of the controller 122 to        terminate the flow of fuel gas 105 to the anode 52 if the        voltage and current outputs is less than the predetermined        amount; and    -   shunting the electrical current by way of the controller 122        between the anode 52 and cathode 53 of the fuel cell 10 if the        voltage and current outputs are less than the predetermined        amount. As disclosed earlier, the method, noted above, is useful        in the first operational condition where decreasing performance        of the fuel cell (either as it relates to predetermined        performance parameters determined in advance, or as compared to        the performance parameters of other fuel cells, or otherwise),        may result in damage to the fuel cell due to increasing heat        accumulation or other unsatisfactory environmental conditions        within the fuel cell 10.

Still further, the present invention provides a method for controllingthe fuel cell 10 which has an anode 52, a cathode 53, a given voltageand current output, and a duty cycle and operating cycle, in a secondoperational condition which includes:

-   -   providing a supply of a fuel gas 105 in fluid flowing relation        relative to the anode 52 of the fuel cell;    -   providing a valve 104 disposed in adjustable fluid metering        relation relative to the supply of the fuel gas 105;    -   providing a controller 122 which is electrically coupled in        current and voltage sensing relation with the anode 52 and the        cathode 53 and which is effective to shunt the electrical        current between the anode and the cathode of the fuel cell, and        which further is coupled in controlling relation relative to the        valve; and    -   after determining the voltage and current output of the fuel        cell, and with the valve being maintained in a position which        insures the substantially continuous supply of fuel gas 105 to        the anode of the fuel cell, periodically shunting, during the        duty cycle, the current between the anode and cathode to cause a        resulting increased electrical power output, and wherein the        operating cycle is about 0.01 seconds to about four minutes, and        wherein the duration of the shunting during the duty cycle is        less than about 20% of the operating cycle.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A fuel cell having an anode and a cathode and which produces anelectrical current having a voltage output, comprising: a controllerelectrically coupled with the fuel cell and which shunts the electricalcurrent between the anode and cathode of the fuel cell; a supply of fuelgas disposed in fluid flowing relation relative to the anode of the fuelcell; and a valve disposed in fluid flowing control relative to thesupply of fuel gas, and wherein the controller is coupled in controllingrelation relative to the valve.
 2. A fuel cell as claimed in claim 1,wherein the controller further comprises voltage and current sensorswhich are disposed in voltage and current sensing relation relative tothe electrical power output of the fuel cell.
 3. A fuel cell as claimedin claim 2, wherein the controller further comprises an electricalswitch having open and closed electrical conditions, and wherein thecontroller upon sensing, by the voltage and current sensors, a voltageand current output of the fuel cell, adjusts the valve into a fluidmetering relationship relative to the supply of fuel gas, and theelectrical switch is positioned in the open or closed electricalcondition, and wherein the fuel cell, in the second condition, has aduty cycle.
 4. A fuel cell as claimed in claim 3, wherein thecontroller, in a first condition, shunts current between anode andcathode of the fuel cell when the electrical switch is in the closedelectrical condition, and wherein the controller simultaneously causesthe valve to terminate the supply of fuel gas to the fuel cell, andwherein the electrical switch when placed in the open electricalcondition by the controller also causes the valve to be placed in acondition which allows the substantially continuous supply of fuel gasto the fuel cell.
 5. A fuel cell as claimed in claim 4, wherein thecontroller, in a second condition, shunts current during the duty cyclebetween the anode and cathode of the fuel cell when the electricalswitch is in the closed electrical condition, and wherein the controllermaintains the valve in a condition which allows the substantiallycontinuous delivery of the fuel gas to the fuel cell during the openingand closing of the electrical switch.
 6. A fuel cell as claimed in claim4, wherein the fuel cell has performance parameters comprising currentand voltage outputs, and wherein the first condition, the voltage andcurrent output of the fuel cell is less than the performance parameters;and wherein in the second condition, the electrical switch periodicallyopens and closes during the duty cycle to cause a resulting increase inthe electrical power output of the fuel cell.
 7. A fuel cell as claimedin claim 4, wherein the fuel cell has performance parameters comprisingcurrent and voltage outputs, and wherein in the first condition, theperformance parameters are declining.
 8. A fuel cell as claimed in claim4, wherein the fuel cell has performance parameters comprising currentand voltage outputs at a full rated current, and wherein in the firstcondition the performance parameters are declining or in a range of lessthan about 0.4 volts.
 9. A fuel cell as claimed in claim 4, wherein thefuel cell has performance parameters comprising current and voltageoutputs, and wherein in the second condition the fuel cell has anoperating cycle of about 0.01 seconds to about 4 minutes, and whereinthe duty and operating cycles are individually and selectively adjustedby the controller at least in part by reference to the performanceparameters of the fuel cell.
 10. A fuel cell as claimed in claim 4,wherein the fuel cell has performance parameters comprising current andvoltage outputs, and wherein in the second condition the fuel cell hasan operating cycle of about 0.01 seconds to about 4 minutes, and whereinthe duty and operating cycles are individually selectively adjusted bythe controller at least in part by reference to the decliningperformance parameters of the fuel cell in relative comparison to theperformance parameters of other fuel cells.
 11. A fuel cell as claimedin claim 4, wherein the fuel cell is serially electrically coupled withanother fuel cell.
 12. A fuel cell as claimed in claim 11, wherein inthe second condition, the fuel cell has a duty cycle and an operatingcycle of about 0.01 seconds to about 4 minutes, and wherein thecontroller is electrically coupled with each of the fuel cells to shuntelectrical current during the duty cycle between the anode and cathodeof each of the fuel cells, and wherein the controller shunts theindividual fuel cells in a given repeating pattern.
 13. A fuel cell asclaimed in claim 12, wherein in the second condition, the controllerwhich is electrically coupled with each of the fuel cells periodicallyshunts electrical current during the duty cycle between the anode andcathode of each of the fuel cells to achieve a resulting increasedelectrical power output from the serially electrically coupled fuelcells, and wherein the given repeating pattern of the controllercomprises serially shunting the individual fuel cells in the repeatingpattern.
 14. A fuel cell as claimed in claim 13, wherein in the secondcondition, the duty and operating cycles are individually selectivelyadjusted to optimize the electrical power output of the fuel cells, andwherein the electrical power output of the serially electricallyconnected fuel cells increases by at least about 5 percent; and whereinthe duration of the shunting during the duty cycle is less than about20% of the operating cycle.
 15. A fuel cell as claimed in claim 14,wherein the electrical switch comprises a field effect transistor, andwherein the controller which is operable to shunt the electrical currentbetween the anode and cathode of each of the fuel cells furthercomprises a passive by-pass electrical circuit which operates uponfailure of the field effect transistor to shunt current between theanode and cathode of each of the fuel cells.
 16. A fuel cell as claimedin claim 15, wherein the passive by-pass electrical circuit comprises adiode.
 17. A fuel cell having an anode and cathode and which produceselectrical power having a current and voltage output, comprising: asupply of fuel gas disposed in fluid flowing relation relative to theanode of the fuel cell; a valve disposed in fluid flowing controllingrelation relative to the supply of fuel gas to meter the fuel gas to theanode of the fuel cell; and a controller electrically coupled with thefuel cell and disposed in controlling relation relative to the valve,and wherein the controller adjusts the valve into a given fluid meteringrelationship relative to the supply of fuel gas, and the controllershunts current between the anode and cathode of the fuel cell.
 18. Afuel cell as claimed in claim 17, wherein the controller furthercomprises voltage and current sensors which are disposed in sensingrelation relative to the electrical power output of the fuel cell; andan electrical switch which has open and closed electrical conditions,and wherein the controller causes the electrical switch to move betweenthe open and closed electrical conditions.
 19. A fuel cell as claimed inclaim 18, wherein the controller, in a first condition, shunts currentbetween the anode and cathode of the fuel cell when the electricalswitch is in the closed electrical condition, and wherein the controllersimultaneously causes the valve to terminate the supply of fuel gas tothe fuel cell, and wherein the electrical switch when placed in the openelectrical condition by the controller also causes the valve to beplaced in a condition which allows the substantially continuous supplyof fuel gas to the fuel cell.
 20. A fuel cell as claimed in claim 19,wherein the controller, in a second condition, shunts current betweenthe anode and cathode of the fuel cell when the electrical switch isplaced in the closed electrical condition, and wherein the controllermaintains the valve in a condition which allows the substantiallycontinuous delivery of the fuel gas to the fuel cell during the open andclosing of the electrical switch, and wherein the fuel cell in thesecond condition has a duty cycle.
 21. A fuel cell as claimed in claim20, wherein the fuel cell has performance parameters comprising currentand voltage outputs, and wherein in the first condition, the voltageoutput of the fuel cell is less than the performance parameters; andwherein in the second condition, the electrical switch periodicallyopens and closes during the duty cycle to cause a resulting increase inthe electrical power output of the fuel cell.
 22. A fuel cell as claimedin claim 20, wherein the fuel cell has performance parameters comprisingcurrent and voltage outputs, and wherein in the first condition, theperformance parameters are declining.
 23. A fuel cell as claimed inclaim 20, wherein the fuel cell has performance parameters comprisingcurrent and voltage outputs at a full rated current, and wherein in thefirst condition the performance parameters are declining or in a rangeof less than about 0.4 volts.
 24. A fuel cell as claimed in claim 20,wherein the fuel cell has performance parameters comprising current andvoltage outputs, and wherein in the second condition the fuel cell hasan operating and duty cycle, and wherein the operating and duty cyclesare individually and selectively adjusted by the controller at least inpart by reference to the performance parameters of the fuel cell.
 25. Afuel cell as claimed in claim 20, wherein the fuel cell has performanceparameters comprising current and voltage outputs, and wherein in thesecond condition the fuel cell has a duty cycle, and an operating cycleof about 0.01 seconds to about 4 minutes, and wherein the operating andduty cycles are individually and selectively adjusted by the controllerat least in part by reference to the declining performance parameters ofthe fuel cell in relative comparison to the performance parameters ofother fuel cells.
 26. A fuel cell as claimed in claim 20, wherein thefuel cell is serially electrically coupled with another cell.
 27. A fuelcell as claimed in claim 26, wherein the controller is electricallycoupled with each of the fuel cells to shunt current between the anodeand cathode of each of the fuel cells.
 28. A fuel cell as claimed inclaim 27, wherein the fuel cell has a duty cycle and an operating cycleof 0.01 seconds to about 4 minutes, and wherein in the second condition,the controller which is coupled with each of the fuel cells periodicallyshunts current during the duty cycle between anode and cathode of eachof the fuel cells to cause a resulting increased electrical power outputfrom the serially electrically coupled fuel cells.
 29. A fuel cell asclaimed in claim 28, wherein in the second condition, the duty andoperating cycles are individually selectively adjusted to optimize theelectrical power output of the respective fuel cells; and wherein theelectrical power output of the serially electrically connected fuelcells increases by at least about 5 percent; and wherein the duration ofthe shunting during the duty cycle is less than about 20% of theoperating cycle.
 30. A fuel cell as claimed in claim 29, and wherein theelectrical switch comprises a field effect transistor, and wherein thecontroller which is operable to shunt current between the anode andcathode of each of the serially connected fuel cells further comprises apassive by-pass electrical circuit which operates upon failure of thefield effect transistor to shunt current between the anode and cathodeof each of the fuel cells.
 31. A fuel cell as claimed in claim 30, andwherein the passive by-pass electrical circuit comprises a diode, andthe controller is an automated intelligent controller.
 32. A fuel cellhaving an anode, a cathode and which produces electrical current havingan electrical power output, comprising: a membrane having oppositesides, and wherein the anode is mounted on one side of the membrane, andthe cathode is mounted on the side of the membrane opposite to theanode; a supply of fuel gas disposed in fluid flowing relation relativeto the anode, and a supply of an oxidant gas disposed in fluid flowingrelation relative to the cathode; voltage and current sensors which areindividually electrically coupled with the anode and cathode; a valvedisposed in fluid flowing controlling relation relative to the supply offuel gas to meter the supply of fuel gas to the fuel cell; an electricalswitch electrically coupled with the anode and cathode and which can beplaced into an open and closed electrical condition; a controllercoupled with the electrical switch, valve and the voltage and currentsensors, the controller upon sensing a voltage and current at thevoltage and current sensors causing the valve to be adjusted into afluid metering relationship relative to the supply of fuel gas, and theelectrical switch to assume a predetermined open or closed electricalcondition.
 33. A fuel cell as claimed in claim 32, wherein thecontroller, in a first condition, shunts current between the anode andcathode of the fuel cell when the electrical switch is in the closedelectrical condition, and wherein the controller simultaneously causesthe valve to terminate the supply of fuel gas to the fuel cell, andwherein the electrical switch when placed in the open electricalcondition by the controller causes the valve to be placed in a conditionwhich allows the substantially continuous supply of fuel gas to theanode of the fuel cell.
 34. A fuel cell as claimed in claim 33, whereinthe controller, in a second condition, shunts current between the anodeand cathode of the fuel cell when the electrical switch is placed in theclosed electrical condition, and wherein the controller maintains thevalve in a condition which allows the substantially continuous deliveryof the fuel gas to the fuel cell during the open and closing of theelectrical switch, and wherein the fuel cell, in the second condition,has a duty and operating cycle.
 35. A fuel cell as claimed in claim 34,wherein the fuel cell has performance parameters comprising current andvoltage outputs, and wherein in the first condition, the voltage outputof the fuel cell is less than the performance parameters; and wherein inthe second condition, the electrical switch periodically opens andcloses during the duty cycle to increase the resulting electrical poweroutput of the fuel cell.
 36. A fuel cell as claimed in claim 34, whereinthe fuel cell has performance parameters comprising current and voltageoutputs, and wherein in the first condition, the performance parametersare declining.
 37. A fuel cell as claimed in claim 34, wherein the fuelcell has performance parameters comprising current and voltage outputsat a full rated current, and wherein in the first condition theperformance parameters are declining or in a range of less than about0.4 volts.
 38. A fuel cell as claimed in claim 34, wherein the fuel cellhas performance parameters comprising current and voltage outputs, andwherein in the second condition the operating cycle is about 0.01seconds to about 4 minutes, and wherein the duty and operating cyclesare individually and selectively adjusted by the controller at least inpart by reference to the performance parameters of the fuel cell.
 39. Afuel cell as claimed in claim 34, wherein the fuel cell has performanceparameters comprising current and voltage outputs, and wherein in thesecond condition the operating cycle is about 0.01 seconds to about 4minutes, and wherein the duty and operating cycles are individually andselectively adjusted by the controller at least in part by reference tothe declining performance parameters of the fuel cell in relativecomparison to the performance parameters of other fuel cells.
 40. A fuelcell as claimed in claim 34, wherein the fuel cell is seriallyelectrically coupled with another fuel cell.
 41. A fuel cell as claimedin claim 40, wherein the controller is electrically coupled with each ofthe fuel cells to shunt current between the anode and cathode of each ofthe fuel cells.
 42. A fuel cell as claimed in claim 41, wherein in thesecond condition, the controller which is coupled with the anode andcathode of each of the fuel cells shunts current during the duty cyclebetween the anode and cathode of the respective fuel cells to achieveincreased electrical power output from the serially electrically coupledfuel cells.
 43. A fuel cell as claimed in claim 42, wherein in thesecond condition, the duty and operating cycles are individually andselectively adjusted to optimize the electrical power output of theresponsive fuel cells; and wherein the electrical power output of theserially electrically connected fuel cells increases by at least about5%; and wherein the duration of the shunting during the duty cycle isless than about 20% of the operating cycle.
 44. A fuel cell having ananode, a cathode and which produces a current having an electrical poweroutput, comprising: a membrane having opposite sides, and wherein theanode is mounted on one side, of the membrane, and the cathode ismounted on the side of the membrane opposite to the anode; a supply offuel gas disposed in fluid flowing relation relative to the anode, and asupply of an oxidant gas disposed in fluid flowing relation relative tothe cathode; voltage and current sensors which are individuallyelectrically coupled with the anode and cathode; a valve disposed influid flowing controlling relation relative to the supply of fuel gas tometer the supply of fuel gas to the fuel cell; an electrical switchelectrically coupled with the anode and cathode and which can be placedinto an open and closed electrical condition; and a controller coupledwith the electrical switch, valve and the voltage and current sensors,the controller upon sensing a voltage and current at the voltage andcurrent sensors causing the valve to be adjusted into a fluid meteringrelationship relative to the supply of fuel gas, and the electricalswitch to assume an open or closed electrical condition, and wherein thecontroller, in a first condition, shunts current between the anode andcathode of the fuel cell when the electrical switch is in the closedelectrical condition, and simultaneously causes the valve to terminatethe supply of fuel gas to the anode of the fuel cell, and wherein theelectrical switch when placed in the open electrical condition by thecontroller causes the valve to be placed in a condition which allows thesubstantially continuous supply of fuel gas to the anode of the fuelcell; and wherein the controller, in a second condition, shunts currentbetween the anode and cathode of the fuel cell when the electricalswitch is placed in the closed electrical condition, and simultaneouslymaintains the valve in a condition which allows the substantiallycontinuous delivery of the fuel gas to the fuel cell to the anode duringthe opening and closing of the electrical switch.
 45. A fuel cell asclaimed in claim 44, wherein the fuel cell in the first and secondconditions has performance parameters comprising selected current andvoltage outputs, and wherein the first condition, the voltage output ofthe fuel cell is less than the performance parameters; and wherein thefuel cell has a duty cycle, and wherein in the second condition, theelectrical switch periodically opens and closes during the duty cycle tocause a resulting increase in the electrical power output of the fuelcell.
 46. A fuel cell as claimed in claim 44, wherein the fuel cell hasperformance parameters comprising current and voltage outputs, andwherein in the first condition, the parameters are declining.
 47. A fuelcell as claimed in claim 44, wherein the fuel cell has performanceparameters comprising current and voltage outputs at a full ratedcurrent, and wherein in the first condition the performance parametersare declining or in a range of less than about 0.4 volts.
 48. A fuelcell as claimed in claim 44, wherein the fuel cell has performanceparameters comprising selected current and voltage outputs, and whereinin the second condition the fuel cell has an operating cycle of about0.01 seconds to about 4 minutes, and wherein the duty and operatingcycles are individually and selectively adjusted by the controller atleast in part by reference to the performance parameters of the fuelcell.
 49. A fuel cell as claimed in claim 44, wherein the fuel cell hasperformance parameters comprising current and voltage outputs, andwherein in the second condition the fuel cell has an operating cycle ofabout 0.01 seconds to about 4 minutes, and wherein the duty andoperating cycles are individually and selectively adjusted by thecontroller at least in part by reference to the declining performanceparameters of the fuel cell in relative comparison to the performanceparameters of other fuel cells, and wherein the duration of the shuntingduring the duty cycle is less than about 20% of the operating cycle. 50.A fuel cell as claimed in claim 44, wherein the fuel cell has a dutycycle and an operating cycle of about 0.01 seconds to about 4 minutes;and wherein the electrical power output of the serially electricallyconnected fuel cells increases by at least about 5%.
 51. A fuel cell asclaimed in claim 44, wherein the fuel cell is serially electricallycoupled with another fuel cell.
 52. A fuel cell as claimed in claim 44,wherein the controller is electrically coupled with the anode andcathode of each of the fuel cells to shunt current between the anode andcathode of each of the fuel cells.
 53. A fuel cell as claimed in claim44, wherein the controller which is coupled with each of the fuel cellsperiodically opens and closes the electrical switch to shunt currentbetween the anode and cathode of each of the fuel cells to cause aresulting increased electrical power output from the seriallyelectrically coupled fuel cells.
 54. A fuel cell as claimed in claim 44,wherein the electrical switch comprises a field effect transistor, andwherein the controller further comprises a passive by-pass electricalcircuit which operates upon failure of the field effect transistor toshunt current between the anode and cathode of each of the fuel cells.55. A fuel cell as claimed in claim 54, wherein the by-pass electricalcircuit comprises a diode.
 56. A plurality of fuel cells which areserially electrically connected together and which individually producevoltage and current outputs comprising: a membrane having opposite sidesand which is made integral with each of the fuel cells, and wherein ananode is mounted on one side of the membrane, and a cathode is mountedon the side of the membrane opposite to the anode; a supply of fuel celldisposed in fluid flowing relation relative to the anode of each of fuelcells, and a supply of an oxidant fuel disposed in fluid flowingrelation relative to the cathode of each of the fuel cells; voltage andcurrent sensors which are individually electrically coupled with theanode and cathode of each of the fuel cells and which sense theelectrical power output of each of the fuel cells; a valve disposed influid flowing controlling relation relative to the supply of fuel gas tometer the supply of fuel gas to each of the fuel cells. ; an electricalswitch electrically coupled with the anode and cathode of each of thefuel cells and which can be placed into an open and closed electricalcondition; and a controller coupled with each of the electricalswitches, valves and the voltage and current sensors, the controlleroperable to adjust the respective valves into a fluid meteringrelationship relative to the supply of fuel gas, and one or more of theelectrical switches to assume an open or closed electrical conditionrelative to one or more of the fuel cells under operational conditions,and wherein the controller, in a first operational condition, uponsensing, at one or more of the fuel cells of interest a voltage andcurrent output at the voltage and current sensors electrically coupledwith same, shunts current between the anode and cathode of the fuel cellof interest when the electrical switch is in the closed electricalcondition, and wherein the controller simultaneously causes the valvewhich is coupled to the fuel cell of interest to terminate the supply offuel gas to the anode of the fuel cell of interest, and wherein theelectrical switch when placed in the open electrical condition by thecontroller causes the valve coupled to the fuel cell of interest to beplaced in a condition which allows the substantially continuous supplyof fuel gas to the fuel cell of interest; and wherein the controller, ina second operational condition, shunts current between the anode andcathode of the fuel cell of interest when the electrical switch isplaced in the closed electrical condition, and wherein the controllermaintains the valve coupled with the fuel cell of interest in acondition which allows the substantially continuous delivery of the fuelgas to the fuel cell of interest during the open and closing of theelectrical switch.
 57. A fuel cell as claimed in claim 56, wherein thefuel cell has a duty and operating cycle, and wherein in the first andsecond conditions the fuel cell has performance parameters comprisingselected current and voltage outputs, and wherein in the firstcondition, the current and voltage outputs of the fuel cell are lessthan the performance parameters; and wherein in the second condition,the electrical switch periodically opens and closes during the dutycycle to increase the electrical power output of the fuel cell.
 58. Thefuel cell as claimed in claim 56, wherein the fuel cell has a duty andoperating cycle, and wherein in the first and second conditions the fuelcell has performance parameters comprising a current and voltage output,and wherein in the first condition, the performance parameters aredeclining.
 59. A fuel cell as claimed in claim 56, wherein the fuel cellhas a duty cycle, and wherein in the first and second conditions, thefuel cell has performance parameters comprising current and voltageoutputs at a full rated current, and wherein in the first condition theperformance parameters are declining or in a range of less than about0.4 volts.
 60. A fuel cell as claimed in claim 56, wherein the fuel cellhas a duty and operating cycle, and wherein in the first and secondconditions the fuel cell has performance parameters comprising currentand voltage outputs, and wherein the operating cycle is about 0.01seconds to about 4 minutes, and wherein the duty and operating cyclesare adjusted by the controller at least in part by reference to theperformance parameters of the fuel cell.
 61. A fuel cell as claimed inclaim 56, wherein the fuel cell has a duty cycle, and wherein in thefirst and second conditions, the fuel cell has performance parameterscomprising current and voltage outputs, and wherein in the secondcondition the fuel cell has an operating cycle of about 0.01 seconds toabout 4 minutes, and wherein the duty cycle and operating cycle areindividually and selectively adjusted by the controller at least in partby reference to the declining performance parameters of the fuel cell inrelative comparison to the performance parameters of other fuel cells.62. The fuel cell as claimed in claim 60, wherein in the secondcondition, the duty and operating cycles are individually selectivelyadjusted to optimize the electrical power output of the fuel cells, andwherein the electrical power output of the serially electricallyconnected fuel cell increases by at least about 5%; and wherein theduration of the shunting during the duty cycle is less than about 20% ofthe operating cycle.
 63. A fuel cell as claimed in claim 56, wherein theelectrical switch comprises a field effect transistor, and wherein thecontroller further comprises a passive by-pass electrical circuit whichoperates upon failure of the field effect transistor to shunt currentbetween the anode and cathode of each of the fuel cells.
 64. A fuel cellas claimed in claim 56, wherein the by-pass electrical circuit comprisesa diode.
 65. A method for controlling a fuel cell which has an anode anda cathode, and a voltage and current output, comprising: determining thevoltage and current output of the fuel cell; shunting electrical currentbetween the anode and cathode of the fuel cell under operationalconditions; providing a supply of a fuel cell in fluid flowing relationrelative to the anode of the fuel cell; providing a valve disposed influid metering relation relative to the supply of the fuel gas; andproviding a controller which is electrically coupled with the anode andthe cathode and which is effective to shunt the electrical currentbetween the anode and the cathode, and which further is coupled incontrolling relation relative to the valve.
 66. A method as claimed inclaim 65, and wherein the fuel cell has performance parameters, andwherein in a first condition the method further comprises: determiningby way of the controller the voltage and current output of the fuelcell; adjusting the valve, by way of the controller, to terminate theflow of the fuel gas to the anode when the voltage and current outputsof the fuel cell are less than the performance parameters; and shuntingthe current between the anode and the cathode by way of the controller.67. A method as claimed in claim 66, wherein the fuel cell hasperformance parameters, and wherein in a second operational conditionthe method further comprises: determining, by way of the controller, thevoltage and current output of the fuel cell; supplying the fuel cellsubstantially continuously with the fuel gas; and periodically shuntingthe current between the anode and the cathode, by way of the controller,to cause a resulting increased electrical power output of the fuel cell,and wherein the periodic shunting of the current comprises the dutycycle of the fuel cell.
 68. A method as claimed in claim 67, wherein inthe second operational condition the controller periodically shunts thecurrent between the anode and the cathode during an operating cyclewhich is about 0.01 seconds to about four minutes in duration.
 69. Amethod as claimed in claim 68, wherein in the second operationalcondition, the duration of the shunting during the duty cycle is lessthan about 20% of the operating cycle.
 70. A method as claimed in claim69, wherein in the second operational condition the voltage output ofthe fuel cell increases by at least 5%.
 71. A method for controlling afuel cell which has an anode and a cathode, and a voltage and currentoutput, comprising: providing a supply of a fuel gas in fluid flowingrelation relative to the anode of the fuel cell; providing a valvedisposed in fluid metering relation relative to the supply of the fuelgas; providing a controller which is electrically coupled in voltage andcurrent sensing relation with the anode and the cathode and which iseffective to shunt the electrical current between the anode and thecathode, and which further is coupled in controlling relation relativeto the valve; determining by way of the controller whether the voltageand current output of the fuel cell has a voltage and current output;after the step of determining the voltage and current output, adjustingthe valve by way of the controller to terminate the flow of fuel gas tothe anode if the voltage and current output is less than a predeterminedamount, and shunting the electrical current by way of the controllerbetween the anode and cathode of the fuel cell.
 72. A method forcontrolling a fuel cell which has an anode, a cathode, a voltage andcurrent output, and a duty and operating cycle, comprising: providing asupply of a fuel gas in fluid flowing relation relative to the anode ofthe fuel cell; providing a valve disposed in adjustable fluid meteringrelation relative to the supply of the fuel gas; providing a controllerwhich is electrically coupled in voltage and current sensing relationwith the anode and the cathode and which is effective to shunt theelectrical current during the duty cycle between the anode and thecathode of the fuel cell, and which further is coupled in controllingrelation relative to the valve; and after determining the voltage andcurrent output of the fuel cell, and with the valve being maintained ina position which insures the substantially continuous supply of fuel gasto the anode of the fuel cell, periodically shunting, by way of thecontroller, the current between the anode and the cathode to cause aresulting increased electrical power output, and wherein the operatingcycle is about 0.01 seconds to about 4 minutes, and wherein the durationof the shunting during the duty cycle is less than about 20% of theoperating cycle.
 73. A fuel cell having an anode, a cathode, and whichproduces an electrical current having a voltage output comprising: acontroller electrically coupled to the fuel cell and which periodicallyshunts the electrical current between the anode and cathode of the fuelcell, and wherein the fuel cell has an operating cycle and a duty cycle,and wherein the periodic shunting increases the electrical power outputof the fuel cell, and the duration of the shunting during the duty cycleis less than 20% of the operating cycle.
 74. A method of bypassing afailing fuel cell, in a fuel cell power system, the fuel cell having ananode, and a cathode, the method comprising placing a diode in parallelwith the fuel cell, the diode having an anode, and a cathode byelectrically coupling the anode of diode to the anode of the fuel cell,and electrically coupling the cathode of the diode to the cathode of thefuel cell, and wherein if the fuel cell fails, current flows from theanode of the fuel cell to the cathode of the fuel cell via the diodeinstead of through the fuel cell.
 75. A fuel cell power systemcomprising: a first fuel cell having an anode and a cathode; a diodehaving an anode coupled to the anode of the first fuel cell and acathode coupled to the cathode of the first fuel cell; and a pluralityof additional fuel cells electrically coupled with the first fuel cell,the additional fuel cells each having an anode and a cathode.
 76. A fuelcell power system comprising: a first fuel cell having an anode and acathode; a diode having an anode coupled to the anode of the first fuelcell and a cathode coupled to the cathode of the first fuel cell; aplurality of additional fuel cells electrically coupled with the firstfuel cell, the fuel cells each having an anode and a cathode; and aplurality of additional diodes having anodes electrically coupled to theanodes of the additional fuel cells, respectively, and having cathodeselectrically coupled to the cathodes of the additional fuel cells,respectively.
 77. A fuel cell power system comprising: a first fuel cellhaving an anode and a cathode; a first diode having an anode coupled tothe anode of the first fuel cell and a cathode coupled to the cathode ofthe first fuel cell; a second fuel cell serially electrically coupledwith the first fuel cell, the second fuel cell having an anode and acathode; and a second diode having an anode coupled to the anode of thesecond fuel cell and a cathode coupled to the cathode of the second fuelcell.
 78. A fuel cell power system in accordance with claim 75 whereinthe diode is a Shottky barrier diode.
 79. A fuel cell power system inaccordance with claim 76 wherein the first mentioned diode and theadditional diodes are Shottky barrier diodes.
 80. A fuel cell powersystem in accordance with claim 77 wherein the first and second diodesare Shottky barrier diodes.